Originally Posted by
ala_xfire
Well, you ain't talking about me, I don't know Jack !!
( at least that's what my wife keeps telling me, but she does call me a jackleg mechanic at times )
I kept it clean, I'm used to the expression, you know jack ***** about it. Meaning you know nothing about it. Variations on an expression that you have cited.
If someone says you know jack about it, you'll get a hint of what they mean.